Thermal relay



March 15,1927.

W. M. BRADSHAW THERMAL RELAY Filed Nov.

l INVENTOR y VVHHam IVI. Bradshaw.

WITN ESSES:

ATTORNEY member and a contact member.

Patented Mar. 15, 1927-.

UNITED STATES PATENT OFFICE.

I WILLIAM I. BBADSEAW, OF WILXINSBUBG, PENNSYLVANIA, ASSIGNOB.l T0 WEISTDTG- HOUSE' ELECTRIC VAN'IA.

' IAvNUlAOTUBING-COMPANY, A CORPORATION 0F PENNSYL- RELAY.

Application med November 5, 1828. Serielle. 672,831.

My invention relates to electrical protective devices and morev particularly to ther mal relays. g

One object of my invention is to provide a thermal relay that shall have `such a time interval in the o eration thereof asto afford protection to e ectrical apparatus against continued overloads. A

` Another object of my invention is to provide a thermal relay, of `the cartridge type and of the above indicated character, that shall have means whereby its contact members are quickly actuated in both' the opening and closing operations under predetermined conditions.

Anotherobject of my invention is to provide a thermal relay, of the above indicated character, -in which a unitary adjusting device controls both the. contact member and the magnetic member. Y

A further object of my inventionis .to provide a thermal relay, ofthe above indicated character, that shall be compact in form, relatively inexpensive rto construct,

" and reliable and effective in itsoperation.

In ythe preferred form, m invention comprises an enclosed cylindrlcal casing with connecting ferrules at the ends thereof. A base memberthat is 'operatively connected between the ferrules supports a bimetallic The contact member is so mountedfthat the free end ofthe bimetallic member, at certain points .op its path of travel, engages the contact member, causing it to engage or disengage a second contact member. Thissecond contact member, together with a permanent .magnet is mounted on a member pivotallyl connected to the base member, electrically insulated therefrom. v

In the engaged position of the contac members, the ends of the 'permanent magnet are in lenga ement with an armature vthat is mounte on the movable contact member, and an adjusting screw is provided to move the reeend. of the pivotally mounted membertoward or away from the base member, thereb simultaneously adjusting the contactmem r and the permanent mag net. With this arrangement, operation of the bimetallic member effects uick actuation of the movable contact mem r.

In the accompan ing drawings:

Figure 1 is a, si view, partially in eleand insulatin vation and partiallyv in section, of the thermal relay embodying my invention, together with a diagrammatic view of. the electrical circuits illustrating the' applicatie- 1 of my invention to the protection of electrical apparatus.

Figure 2 is a view, partially in plan and partially in section, of the thermal relay shown in Fig. 1.

Referring to Figures 1 and2 ofthe drawing, a relay 1, embodying my invention, comprises a cylindrical casing 2 which is provided with a ferrule 3 at one-end, and, at the other end, with a ferrule` 4 having an opening 5 therein. A base member v6 is rigidly secured to the ferrule 3 by screws 7 and it supports a bimetallic member 8 and a resilient member v9 that is normally biased away from the base member 6 and supports a contact member 10. A brace member 11 gives rigidity to the structure by being securedI lirmly to the ferrule 4 by bolts 12, and to the bimetallic member 8 and the base member 6 by rivets 13.. The rivets 13 are electrically insulated from the brace member 11, the bimetallic member 8, and the base member 6 by means of'insulating washers 14 bushings 15. f

A longitudlnal slot 16 divides the bimetallic member 8 into two parts 17 and 18. The part 17 is electrically insulated from the base member 6 by means of an insulating member; 19, but is in electrical engagement with the brace member 11, while the part 18 is in electrical engagement with the `base member 6, but is insulated from the vmember 8 is held together by means of a clamp member 22, having an insulating lining 23.

A bracket member 24 is mounted on the base member 6 by a screw-25, but is electrically insulated therefrom by means of an insulating member 26. The screw 25 is electrically insulated from the bracket member 24 by means of a flanged insulating bushing 27.- The bracket member 24 extends through the opening 5 in the ferrule 4, but is electrically msulated from the ferrule by means of an insulating bushing 28. The outer end of the bracket member 24 carries a terminal screw 29. A member 31 isA pivotall'y Yconnected to the bracket'member 24 by means of a hinge'pin 32, and supports van adjustable contact member 33 and a permanent magnet 36.

The contact member 33 is so threaded, as at 34as to be adjustable with respect to the pivotally mounted member 31, and extends through an opening 35 in the base member 6. The permanent magnet 36 is secured to the ivotally mounted member 31 by a screw 37, but is electrically insulated therefrom by means of an insulating member .38. The screw 37 is electrically insulated from the magnet 36, by means of a flanged insulating .bushing 39. The pole pieces of the magnet 36e'xtend through an opening 41 in the base member 6 and engage an armature member 42 that is rigidly secured to the resilient vmember 9. .The member 31-and the members carriedl thereby, may be adjusted relatively to the member 6l by a screw 42a that'. has` screw. threaded lengagement with theA member 6 and is electrically insulated from the member 31 by a collar 426, which collar is mounted on a reduced end portion of 'the member 42aand is located in a iiotch'420 in .the member 31. A l p Referring. to the diagrammatic view of the electrical circuit shown in Figure 1 a source of electrical energy 43 is connected in circuit v with the thermal relay 1, a circuit breaker The thermal relay is shown in the drawings .in its circuit-closing condition, the con-- tact members 10 and'33 being in engagement. Under this condition, an electric circuit is completed comprising the source of energy 43, ferrule 3, base member .6, contact members 10 and 33, resilient member 9, pivotally mounted memberl 31, bracket member' 24,

terminal screw'29, vand the coil vof the elecy tromagnet 49.

With the coil ofthe electromagnet 49 thus energized, theciraziuitbreaker 44 is held in its closed position, as shown, permitting current to traverse' the main circuit extending .from .the source of energy 43, through the ferrule 3,2 the base member 6, bimetallic member 8 from the thereof,.the brace member 11, ferrule 4, and circuit breaker 44 t'o the electrical apparatus 45.

When current traverses the lbimetallic member 8, its temperature is increased t0v thereby cause its ,free end to move away from the base member 6. rIf the'current exceeds a predetermined value, the bimetallic member part 18 to the part 17 8 will, after a predetermined interval of time, attain such temperature that its free end will'move far enough to engage a U- shape portion on the resilient member 9 to thus cause the contact member 10 to disengage the contact member 33.

When the bimetallic member 8 engages the U-shape portion of the member 9, the

cuit ofthe apparatus 45 to be protected.

y When no current traverses the main circuit the temperature of the apparatus 45 falls, as does also that of the bimetallic member 8. When the temperature ofthe bimetallic member 8 has fallen to such degree that this member has substantially returned to its ineffective position, the armature member 42 secured to the contact member 9 is ,forced into close proximity to the pole pieces of the magnet 36. When a certain yproximity is attained, the'magnetic force is sulicient to overcome the resiliency of the member 9 and the armature member 42 rapidly engages the pole pieces of the magnet 36, thereby bringing the contact member 10 rapidly into engagement with the contact member. 33, and reclosing the electric circuit through the operating coil of the electromagnet 49. This coil then actuates the armature .member 48 to vclose the circuit breaker 44, thereby restoring the electric circuit extending through the apparatus 45 to its normal: or closed, condition.

The thermal relay embodying my invention is adapted to be constructed as a cartridge-type relay and in this form it may be installed in standard cartridge-fuse clips. The mechanism ofthe relay is' a unit and may be secured to the ferrules of the cartridge-type casing by easily removable end screws, thus providing ease of inspection and adjustment.

I My invention is not limited to the appli` cations illustrated nor to the structure of the relay as described above, as various modifications may be made'therein, and it may be adapted to protect various devices without departing from the spirit and scope of the invention, as set forth -in the appended claims.

I claim as my invention: y

1. Athermal relay for4 electrical apparatus comprising'a bimetallic member freely.

movable through a, definite path, a relatively .movable contact member and magnetic means co-operating withtliecontact member to cause the bunetallic member to actuate the contact member with a snap action when jt reaches substantially either end of its path of free movement, corresponding to a predetermined temperature of the bimetallic member.

2. A thermal relay for electrical apparatus comprising' a bimetallic member freely movable through a definite path, relatively movable contact members for controlling an electric circuit under predetermined conditions, and magnetic means whereby one contact memberis rendered positively inoperative While the bimetallic member i s traveling through its path of free movement.

3. A thermal relay of the cartridge-fuse type, comprising a tubular casing of electric-insulating material, metal errules at the ends of said casing, a bimetallic member in said casing electrically connected to the metal errules and having one end freely l movable through a definite path, a fixed contact member, a contact member movableby said bimetallic member at the ends of its f free movement, and means operatively associated with said contact members for eiecting engagement and disengagement of. said contact members by said bimetallic member with a snap action.

4. A thermal relay of the cartridge-fuse type comprising a tubular casing of electric-insulatingl material, metal errules at the respective ends thereof, a base member having one end secured to one or said ferrules, a bimetallic member supported by the other end of said base member having its ends electrically connected respectively to said base member and to the second errule, the free end of said bimetallic member being freely movable through a definite' path, a ixed and a movable contact member 'operatively supported by said base member, and

means operatively supported by said base member for eecting r isengagement of said contact members by said bimetallic member lnsulating material, metallic ferrules at the ends of said casing, a base member supported by andfin electricalI connection with one of said errules, a bimetallic member supported by said base member and in electrical connection with said base member and the other ferrule, a spring member for yieldingly limiting the free movement of one end of the bimetallic member, contact members adapted to be engaged and disengaged by movement of said spring member, and magnetic means associated Vwith said contact members for so controlling the, same that said engagement and disengagement is effected with a snap action.

6. A thermal relay of the cartridge-fuse type comprising a tubular casing of electricinsulating material, metallic errules at the ends of said casing, a base member supported by and in electrical connection with one of said ferrules, a bimetallic member supported by said base member and in electrical connection with said base member and the other ferrule, a spring member for yieldingly limitin the free movement of one end of the bimeta lic member, a movable Contact member carried by said spring member, a second contact member, a magnetic member which holds the two contact members in engagement under predetermined conditions. and a means for operatively supporting said second contact member and said magnetic member and for permitting of their simultaneous adjustment relatively to the movable'contact member.

ln testimony whereof, li have hereunto subscribed my name this 29th day of 0ctober, 1923.

WILLIAM M. BRADSHAlV. 

